Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels and using a suitable end effector, may be used to cut, dissect, elevate, coagulate or cauterize tissue, or to separate muscle tissue off bone. Ultrasonic instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from an ultrasonic transducer, through a waveguide, to the surgical end effector. Such instruments may be used for open procedures or minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end effector is passed through a trocar to reach the surgical site.
Activating or exciting the end effector (e.g., cutting blade) of such instruments at ultrasonic frequencies induces longitudinal vibratory movement that generates localized heat within adjacent tissue, facilitating both cutting and coagulation. Because of the nature of ultrasonic instruments, a particular ultrasonically actuated end effector may be designed to perform numerous functions, including, for example, cutting and coagulating.
Ultrasonic vibration is induced in the surgical end effector by electrically exciting a transducer, for example. The transducer may be constructed of one or more piezoelectric or magnetostrictive elements in the instrument hand piece. Vibrations generated by the transducer section are transmitted to the surgical end effector via an ultrasonic waveguide extending from the transducer section to the surgical end effector. The waveguides and end effectors are designed to resonate at the same frequency as the transducer. Therefore, when an end effector is attached to a transducer the overall system frequency is the same frequency as the transducer itself.
The amplitude of the longitudinal ultrasonic vibration at the tip, d, of the end effector behaves as a simple sinusoid at the resonant frequency as given by:d=A sin(ωt)where:    ω=the radian frequency which equals 2π times the cyclic frequency, f; and    A=the zero-to-peak amplitude.The longitudinal excursion is defined as the peak-to-peak (p-t-p) amplitude, which is just twice the amplitude of the sine wave or 2A.
Solid core ultrasonic instruments may be divided into two types, single element end effector devices and multiple-element end effector. Single element end effector devices include instruments such as scalpels and ball coagulators. Multiple-element end effectors may be employed when substantial pressure may be necessary to effectively couple ultrasonic energy to the tissue. Multiple-element end effectors such as clamping coagulators include a mechanism to press tissue against an ultrasonic blade. Ultrasonic clamp coagulators may be employed for cutting and coagulating tissue, particularly loose and unsupported tissue. Multiple-element end effectors that include an ultrasonic blade in conjunction with a clamp apply a compressive or biasing force to the tissue to promote faster coagulation and cutting of the tissue, with less attenuation of blade motion.
Orthopedic surgery or orthopedics is the branch of surgery concerned with acute, chronic, traumatic, and overuse injuries and other disorders of the musculoskeletal system. Orthopedic surgeons address most musculoskeletal ailments including arthritis, trauma and congenital deformities using both surgical and non-surgical means. Orthopedic procedures include hand surgery, shoulder and elbow surgery, total joint reconstruction (arthroplasty), pediatric orthopedics, foot and ankle surgery, spine surgery, musculoskeletal oncology, surgical sports medicine, and orthopedic trauma. These procedure often require the use of specialized surgical instruments to treat relatively softer musculoskeletal tissue (e.g., muscle, tendon, ligament) and relatively harder musculoskeletal tissue (e.g., bone). Quite often, these orthopedic surgical instruments are hand operated and a single procedure may require the exchange of a number of instruments. It may be desirable, therefore, for a variety of electrically powered and unpowered ultrasonic instruments to perform these orthopedic surgical procedures with more efficiency and precision than is currently achievable with conventional orthopedic surgical instruments while minimizing the need to exchange instruments when cutting, shaping, drilling different types of musculoskeletal tissue.